Pyrolysis reactors have been used in refineries or chemical plants to produce olefinic materials (e.g., ethylene and propylene) from various hydrocarbon feeds for petrochemicals manufacture. The feeds for this type of reactor typically range from ethane to vacuum gas oil, with heavier feeds giving higher yields of additional by-products, such as naphtha.
Pyrolysis reactors have also been used to produce alkynes, such as acetylene. As an example, U.S. Pat. No. 7,943,808 describes a reverse-flow regenerative reactor utilized in the manufacture of acetylene and other higher hydrocarbons from a methane feed. This type of reactor uses a series of bed packings to heat up and quench streams passing through the reactor. However, this process relied upon the bed packings to provide the quench (e.g., via indirect quenching).
As an alternative approach, U.S. Pat. No. 2,319,679 to Hasche describes a pyrolysis reactor that can be used to produce acetylene containing product at low pressure. In this process, the reactor is a regenerative reverse flow type reactor, which stores heat in tiles or bricks for carrying out the pyrolysis of the methane feed. Then, the feed is quenched with a water quench after passing through a single bed packing of bricks or tiles. In this process, longer cycles are utilized for the heating step and the pyrolysis step, which are two or more minute cycles. Disadvantageously, these longer cycles result in lower selectivity and increased buildup of tar and coke within the reactor, which is difficult to remove based at least on the extended exposure to heat.
U.S. Pat. No. 8,013,196 to Mamedov describes a two-stage pyrolysis scheme that is used to convert methane containing feed to acetylene. The acetylene is then in situ hydrogenated into ethylene using a higher alkane as a hydrogen transfer medium. Oxygen is fed to the pyrolysis reactor along with the methane to produce a combustion reaction in the pyrolysis reactor. As a result of the oxygen co-feed, substantial amounts of H2O and CO are produced in the pyrolysis product. These undesired byproducts have to be separated from the desired products, which increase the complexity and costs associated with the process. Further, the substantial amounts of H2O and CO react with the hydrocarbons to lessen the efficiency of the process.
There is a desire to enhance pyrolysis reaction processes to produce greater quantities of unsaturated hydrocarbons, and lesser quantities of undesired by-products, such as H2O, CO, and CO2. In particular, there is a desire to produce quantities of unsaturated hydrocarbons, such as acetylene, that can be readily converted to ethylene. As economics tends to further favor heavier feeds for pyrolysis processes, there is also a desire to develop enhanced pyrolysis processes that are more readily capable of handling a wider variety of hydrocarbon feeds than conventional processes. There is also a desire for enhancing pyrolysis reaction processes to increase the production of acetylene and/or ethylene in the pyrolyzed product, while also reducing the problems associated with coke and tar build-up. Furthermore, there is a desire to convert some of the acetylene product to ethylene within the pyrolysis reactor, as this reduces the complexity of the downstream processes to convert acetylene to ethylene, when ethylene is the desired product.